Conventional processes for recovering copper from copper and/or copper-iron sulfide concentrates involve melting them along with slag-forming ingredients in a reverberatory or flash smelting furnace to produce a copper-iron sulfide matte. This matte is then blown with air, the so-called converting operation, to produce "blister" copper which is subsequently purified by fire refining and then cast into anodes for ultimate electrolytic refining of the copper.
A significant disadvantage in this conventional copper recovery process is that sulfur is emitted as sulfur dioxide at a number of different points in the process. A major portion of the sulfur emitted during reverberatory smelting is at sufficiently low levels of concentration that it is not generally practical to recover the emitted sulfur dioxide for manufacturing by-products such as sulfuric acid, liquid SO.sub.2 or elemental sulfur. This sulfur dioxide is generally discharged into the surrounding atmosphere and hence is wasted. Moreover, the emission of this sulfur dioxide to the atmosphere contributes to deteriorating air quality. Additionally, conventional copper smelting requires that molten matte and slag be transferred by ladle between the converters and the primary smelting unit (e.g., the reverberatory or flash smelting unit). During these transfers, the molten matte and slag phases may fume copiously resulting in the emission of sulfur dioxide into the workplace with all the environmental problems associated therewith. Ventilation and gas cleaning costs associated with ensuring an adequate protection of both the workplace and the environment represent a very substantial cost at present day smelters.
In recognition of the continuing concern to protect the environment and to improve process economics, a number of methods for smelting copper sulfide ores have been proposed in recent years. In this regard, reference is made to U.S. Pat. No. 3,589,892; U.S. Pat. No. 3,799,764; U.S. Pat. No. 2,857,701; and U.S. Pat. No. 4,006,010, as representative of alternate processes directed toward overcoming some of the disadvantages associated with conventional copper sulfide smelting. Notwithstanding the advances which have been made, these processes have limitations and/or disadvantages which are readily apparent to those skilled in the art.
In the process of U.S. Pat. No. 4,006,010, for example, a specifically designed smelting furnace is required, thereby increasing the mechanical complexity for the process which simultaneously decreases the process flexibility. Additionally, the step of preparing a charge for the furnace smelting operation is required, thereby adding to capital equipment needs and processing steps.
In U.S. Pat. No. 3,857,701, reliance is placed upon electric furnace smelting, which again decreases the process flexibility, increases the mechanical complexity of this process, and greatly increases the cost in terms of energy required.
For these and other reasons, there still remains a need for a new and an improved process for treating copper concentrates by pyrometallurgical processes to recover the copper therefrom.